This invention relates to the field of intravascular catheters, and more particularly to the means to sealingly affix catheter components together.
Intravascular balloon catheters such as those used in percutaneous transluminal angioplasty (PTA) and percutaneous transluminal coronary angioplasty (PCTA) generally have an inflatable balloon mounted along the distal region of the catheter, surrounding the catheter shaft. A catheter shaft lumen is configured for the delivery of inflation media to the interior of the balloon, to inflate the balloon once it is positioned at the desired location within the patient's vasculature.
Typically, the balloon catheter has an outer tubular member with a distal extremity terminating within the balloon interior and an inner tubular member with a distal extremity extending through and slightly beyond the distal end of the balloon. The annular space between the inner and outer members defines the inflation lumen in communication with the balloon interior. The integrity of the balloon interior is maintained, thereby enabling the balloon interior to hold inflation media, by fluid tight bonds located at proximal and distal extremities of the balloon which secure the balloon to the outer tubular member and the inner tubular member respectively. However, a variety of catheter designs are known. For example, the balloon can be coextruded with the catheter outer tubular member with a fluid tight bond securing the balloon distal extremity to the inner tubular member. Similarly, a single catheter shaft provided with a plurality of lumens can be used in place of the inner and outer membered shaft.
In the manufacture of balloon catheters, a number of techniques may be used to bond the balloon to the catheter shaft, including use of heat shrinkable balloon material, adhesives or fusion bonding. One attractive method of fusion bonding involves the use of laser energy. In this instance, the balloon and shaft mating surfaces are rapidly heated by a laser at the desired location of the bond. The temperature of the surfaces exposed to the intense and focused heat of the laser beam changes at a rate of approximately 10.sup.10 degrees C. per second. This heat from the application of the laser beam melts the interface of the two surfaces, which fuse together upon subsequently cooling down and a solid fusion bond is formed.
While laser bonding is a known technique for bonding balloons to catheter shafts, see for example U.S. Pat. No. 4,958,634 (Jang) and also U.S. Pat. No. 5,267,959 (Forman), one difficulty has been forming a balloon catheter using laser bonds between immiscible polymeric materials. Laser bonding typically requires the use of polymeric materials which are materially soluble or miscible when in the molten state. For example, materials from the same polymer family, such as polyethylene terephthalate (PET) and HYTREL.RTM. which are both polyesters, will form strong laser bonds together, whereas, PET and nylon will not.
Laser bonding provides bonds suitable for use in balloon catheter manufacture which are fluid tight, and sufficiently strong to withstand the fluid pressures produced by the inflation media which sometimes can exceed 400 psi. Moreover, because laser bonding generally provides superior repeatability in manufacturing, it is a preferred bonding method. However, because the ideal catheter shaft and balloon materials are chosen based on factors such as strength, flexibility and stiffness, the ideal materials are not necessarily compatible polymeric materials capable of being effectively fusion bonded together. Therefore, what has been needed is the ability to fusion bond dissimilar materials together to form the invention claimed, which is a catheter with a fusion bond. The present invention satisfies these and other needs.